born June 19, 1782, Saint-Malo, France
died Feb. 27, 1854, Paris
French priest and philosopher.
With his brother Jean, he sketched a program of church reform in Reflections on the State of the Church (1808) and in 1814 produced a defense of ultramontanism (papal authority). Ordained a priest in 1816, he wrote the acclaimed Essay on Indifference Toward Religion (1817–23), which argued for the necessity of religion. After the July Revolution (1830), he cofounded the journal L'Avenir to advocate democratic principles and church-state separation. Its principles were condemned by the pope in 1832. Lamennais's The Words of a Believer (1834), written in response, provoked another papal encyclical and led to Lamennais's severance from the church. Thereafter he wrote in the cause of republicanism and socialism.